Device for removing impurities from a liquid

ABSTRACT

The invention relates to a device for removing impurities from a liquid, comprising a reservoir ( 2 ) for holding filtering material ( 4 ) at the bottom side ( 3 ) thereof on the one hand and a liquid, in particular at the upper side above the filtering material, on the other hand, a liquid supply channel ( 6 ) opening into the bottom side of the reservoir for supplying liquid to be purified to the reservoir via liquid displacement means, a first liquid discharge channel ( 14 ) extending from the upper side of the reservoir for discharging purified liquid from the reservoir and a fluid supply channel ( 8 ) opening into the bottom side of the reservoir for causing turbulence in filtering material present in the liquid at regular intervals by supplying a fluid, using fluid displacement means, and thus detaching impurities from said filtering material, A pipe ( 10 ) comprising a first end positioned at the bottom side of the reservoir and a second end positioned opposite said first end is provided in the reservoir, spaced from the mouth of the fluid supply channel by some distance, for the passage of a fluid supplied to the reservoir via the fluid supply channel ( 8 ).

The invention relates to a device for removing impurities from a liquid,comprising a reservoir for holding filtering material at the bottom sidethereof on the one hand and a liquid, in particular at the upper sideabove the filtering material, on the other hand, a liquid supply channelopening into the bottom side of the reservoir for supplying liquid to bepurified to the reservoir via liquid displacement means, a first liquiddischarge channel extending from the upper side of the reservoir fordischarging purified liquid from the reservoir and a fluid supplychannel opening into the bottom side of the reservoir for causingturbulence in filtering material present in the liquid at regularintervals by supplying a fluid, using fluid displacement means, and thusdetaching impurities from said filtering material.

More in particular, the invention is intended and in particular suitablefor use with ponds in which (ornamental) fish are present. It isimportant that the water in such ponds retains a particular level ofpurity in spite of the production of manure by the fish. Although suchmanure is decomposed in a fully natural manner by the oxygen in thewater, this natural decomposition is insufficient in particular in thecase of ponds in which a relatively large number of fish are present.Japanese carp, for example, also referred to as Koi, a Japanese term,are known to produce a relatively great deal of manure, whilst Japanesecarp often represent a considerable economic value. For reasons ofanimal well-being, but certainly also because of the economic value thatfish in a pond represent, it is important that additional provisions forpurifying the water be made. It is known to use a biological filteringmaterial, in particular in the form of granules, for this purpose.On:the one hand, such a biological filtering material acts as a catalystin the natural decomposition of manure by oxygen. On the other hand,impurities adhere in the form of a slimy layer to the filteringmaterial, which is usually characterized by a rough outer structure.Because of said adherence of the impurities to the filtering material, acertain degree of saturation of the filtering material occurs, as aresult of which the purifying action of the biological filteringmaterial may quickly deteriorate.

British patent application GB 2,371,244 A describes a two-stage waterpurification system. In the first stage, water from a pond is passedthrough a screen, which retains impurities in the form of particulatematerial in the water. To prevent the screen becoming clogged, a liquidflow past the screen is created, as a result of which the particles aredislodged from the mesh and settle on the bottom, where said particulatematerial can be manually removed. Thus, the water quality is adverselyaffected at first. In the second stage, the pond water to be furtherpurified is carried past a biological filtering material, thus providinga further purification of the water.

An important drawback of this known system is the necessary dimensionthereof, so that the system not only takes up a great deal of space butin addition is relatively costly. Furthermore, the through-flow of thesystem will gradually decrease and be relatively small in practice,whilst in addition the slimy impurities cannot be altogether preventedfrom depositing on the biological filtering material in the long run,resulting in a deteriorated effect thereof.

A device as referred to in the introduction is known from German patentapplication DE-A1-19839161. Said document describes a filtering systemcomprising a reservoir, on the flat bottom of which a granular materialis present, through which water to be filtered is passed. Rinsing aircan be supplied to the filtering material via the bottom of thereservoir so as to clear of the granular filtering material ofimpurities adhering thereto. An important drawback of said filteringdevice is the fact that the degree to which the individual granules ofthe filtering material are subjected to the action of the rinsing aircannot be controlled in any way. Thus, certain granules of filteringmaterial, for example granules present in the corner of the reservoir,are hardly subjected to the action of the rinsing air, if at all, whilstother granules are subjected to the action of the rinsing air more thanis necessary.

The object of the invention is to provide a device as referred to in theintroduction, possibly in preferred embodiments of the invention, thatprovides a solution or at least an improvement as regards the drawbacksof the prior art as described above. In order to accomplish that object,a pipe comprising a first end positioned at the bottom side of thereservoir and a second end positioned opposite said first end isprovided in the reservoir, spaced from the mouth of the fluid supplychannel by some distance, for the passage of a fluid being supplied tothe reservoir via the fluid supply channel. Thus a strongly improvedaction as regards the detaching of (slimy) impurities from thebiological filtering material is achieved. On the one hand this isachieved in that the filtering material present in the pipe is subjectedto a stronger agitating action, in which connection it is noted thatbesides fluid, also the filtering material will pass through the pipe.On the other hand it is possible in this manner to effect a circulationof the filtering material within the reservoir, so that the filteringmaterial will be more evenly subjected to the action of the fluid flowin that the granular material will be driven upwards within the pipe,whilst it will gradually sink again outside the pipe under the influenceof the force of gravity and eventually return to the first end of thepipe. The pipe thus provides a separation between granular filteringmaterial in the pipe and between the mouth and the first end of the pipeon the one hand and the remaining granular filtering material in thereservoir on the other hand, with the former part of the granularmaterial moving away from the mouth and being expressly subjected to theagitating action of the fluid flow, whilst the latter part of thegranular filtering material moves towards the mouth, thus creating theaforesaid circulation. It will be apparent within this framework tothose skilled in the art that various cross-sectional shapes of the pipemay be used, for example circular, square or elongated.

By way of general explanation it is noted that in practice pond water issupplied to the reservoir via the liquid supply channel, whilst purifiedliquid is returned to the pond via the first liquid discharge channel.The strength of the device according to the invention is particularlyits simplicity. Instead of attempting to prevent slimy impurities fromadhering to the biological filtering material, as is the case with thesystem according to GB 2371244 A, such adherence is allowed now.However, before said adherence of slime to the biological filteringmaterial would lead to a substantially decreased purifying actionthereof, said filtering material is agitated by a fluid flowing past,such as a relatively strong liquid flow or a gas flow, more specificallyair bubbles, as a result of which the particulate impurities will becomedetached from the filtering material and be suspended in the liquidabove the filtering material on account of the relatively low specificweight of said impurities. From said suspended condition, theparticulate impurities can be readily discharged. To that end a screenmight be used, for example, which is moved through the liquid by hand,thus catching the suspended impurities.

To facilitate the interception of fluid and filtering material, the pipeis preferably provided with a funnel on the side facing towards themouth of the fluid supply channel, which funnel flares out in thedirection of the mouth of the fluid supply channel.

The second end of the pipe is preferably disposed in the upper side ofthe reservoir in order to prevent the impurities that have been detachedin the pipe from adhering to filtering material again.

In particular in combination with the above preferred embodiment, aresistance element is preferably disposed in the reservoir, spaced fromthe second end of the pipe by some distance and being in line therewith.The resistance element ensures that the filtering material will to alarge extent remain at the bottom side of the reservoir, in spite of theturbulence being produced, so that the discharge of detached impuritiescan take place more quickly, more efficiently and more simply. Inaddition, if a second liquid discharge channel is used, biologicalfiltering material is thus prevented from reaching said second liquiddischarge channel.

A maximum turbulence of the filtering material can be achieved if thefluid supply channel opens into the bottom of the reservoir.

Preferably, the bottom of the reservoir extends upwards from the mouthof the fluid supply channel, since the biological filtering material,assuming that it is in granular form, will sink towards the mouth of thefluid supply channel under the influence of the force of gravity, whereit will be driven away again by the fluid. Thus it is possible, inparticular in combination with the use of a pipe according to the mainaspect of the present invention, to effect a circulation of filteringmaterial within the reservoir.

A very suitable embodiment is obtained if the bottom of the reservoir issubstantially V-shaped, seen in vertical cross-sectional view.

Preferably, the mouth of the fluid supply channel in the reservoir isdirected upwards, so that the impurities that have been detached fromthe filtering material are driven to the upper side of the reservoir,where they will stay longer than the particulate biological filteringmaterial because of their relatively low specific weight.

A convenient manner of discharging impurities that have been detachedfrom the filtering material, which impurities are suspended in theliquid above said filtering material, can be obtained if the devicecomprises a second liquid discharge channel extending from the upperside of the reservoir for discharging liquid with impurities suspendedtherein as a result of the turbulence of the filtering material, andshut-off means for shutting off the first liquid discharge channeland/or the second liquid discharge channel. Such a device ispre-eminently suitable for being operated in a fully automated manner,for example by means of a timer, wherein liquid containing impuritiesthat previously adhered to the biological filtering material aredischarged, for example to a sewer system, via the second liquiddischarge channel during the period that a turbulence is caused in thefiltering material and/or for a short period of time thereafter. Inorder to prevent the suspended contaminations from reaching the pondyet, the shut-off means are provided. Said shut-off means are notnecessarily operative on the first liquid discharge channel, since it isalso conceivable to use a configuration in which liquid, in order toreach the first liquid discharge channel from the reservoir, must passthe inlet of the second liquid discharge channel. By opening said inletof the second liquid discharge channel, using the shut-off means, it canbe arranged that liquid from the reservoir is temporarily unable toreach the first liquid discharge channel.

If a second liquid discharge channel is used, a weir is preferablyprovided between the first liquid discharge channel and the secondliquid discharge channel. Liquid will not flow over said weir until theliquid discharge channel that is located upstream of the weir has beenshut-off by the shut-off means.

In addition to that, the fluid displacement means and the shut-off meansare preferably arranged for joint operation, so that the impurities thathave been detached from the filtering material by the fluid flow cannotunintentionally reach the pond yet.

Because of the inherent presence of pneumatic facilities for supplyingair via the fluid supply channel in those cases in which the fluid beingused is air, it is in particular preferable for the shutoff means tooperate pneumatically, so that the required pneumatic facilities thatare already present can also be used for operating the shut-off means.

Preferably, the shut-off means comprise a membrane, so that pneumaticoperation of the shut-off means can easily be realised.

The invention will now be explained in more detail in the description oftwo preferred embodiments thereof, in which reference is made to thefollowing figures.

FIG. 1 is a schematic, vertical cross-sectional view of a firstembodiment of a device according to the invention.

FIG. 2 is a top plan view of the device of FIG. 1.

FIGS. 3 a and 3 b are sectional views along the line III-III in FIG. 2,showing the unclosed position and the closed position, respectively.

FIG. 4 is a schematic, vertical cross-sectional view of a secondembodiment of a device according to the invention in the stationaryposition of use.

FIG. 5 shows the second embodiment in a rinsing position.

FIG. 1 shows a filtering system 1 comprising a cylindrical reservoir 2having a bottom 3. The bottom 3 is V-shaped, seen in verticalcross-sectional view. Present at the bottom side of the reservoir is agranular biological filtering material 4, whilst the space above saidfiltering material 4 is filled with pond water 5 up to level 17. It willbe understood that water is present also between the grains of thebiological filtering material 4. The supply of water to be purified tothe reservoir 2 takes place via the water supply pipe 6, which isprovided with an annular element 13 at its outflow opening, whichelement extends around the pipe 10 along part of the length thereof. Theannular element 13 is centrally positioned in the biological filteringmaterial 4. The outflow of water takes place either in upward directionor in downward direction via the annular space between the annularelement 13 and the outer side of the pipe 10. The biological filteringmaterial 4 on the one hand provides for the decomposition of impuritiesin the pond water being supplied, whilst on the other hand theimpurities will in part adhere to the biological filtering material 4 inthe form of a slimy layer. The outflow of purified pond water 5 from thereservoir 2 takes place via the outlet opening 7, where a container 19(not shown in FIG. 1) is disposed. Present at the bottom of thecontainer 19 is a circulation pipe 14, which eventually returns thewater to the pond from which it originated, and a discharge pipe 15,which is connected to a sewer system. A weir 16 is disposed between thecirculation pipe 14 and the discharge pipe 15. Disposed above thecirculation pipe 14 is a membrane valve 20, which is not pneumaticallyenergized via a pneumatic pipe 21 during normal use and whichconsequently does not shut off the circulation pipe 14. Because of thepresence of the weir 16, the level of the pond water 5 will remain atthe level indicated at 17 during normal use, at which a dynamic balanceis reached between the supply of pond order to be purified to thereservoir 2 via the water supply pipe 6 and the discharge of purifiedpond water 5 via the circulation pipe 14.

An air supply pipe 8 opens into the point of the V-shaped of the bottom3 at the location indicated by reference numeral 9. The pipe 10 with thefunnel 11 present at the bottom thereof is positioned directly above themouth 9, with the lower end of the pipe 10 being located in the part ofthe reservoir 2 in which the biological filtering material 4 is present,whilst the upper end of the pipe 10 is located in the part of thereservoir 2 in which particularly pond water 5 and no filtering material4 is present. Present above the upper end of the pipe 10, spacedtherefrom by some distance, is a disc-shaped check member 12.

The operation of the filtering system 1 is as follows. During normaluse, pump means (not shown) circulate pond water from a pond via thewater supply pipe 6 to the biological filtering material 4, where thepurification process, which is known per se, takes place. Then the wateris returned to the pond in question via the outlet 7 and the circulationpipe 14. During this process, slimy impurities will gradually adhere tothe granular biological filtering material 4. To remove these impuritiesand thus maintain the purifying action of the biological filteringmaterial 4 at the required standard, air is supplied to the reservoir 2via the air supply pipe 8 for one or more minutes each day, depending onthe expected degree of contamination of the filtering material 4. At thesame time, the membrane valve 20 will be energized, as a result of whichthe circulation pipe 14 is shut off. Since water continues to besupplied from the pond (not shown) via the water supply pipe 6, thelevel of the pond water 5 in the reservoir 2 will rise from the levelindicated at 17 to a higher level indicated at 18, which is the samelevel as the level of the upper side of the weir 16. When the supply ofpond water to the reservoir 2 via the supply pipe 6 is continued, waterwill flow over the weir 16, which water will be discharged via thedischarge pipe 15. This part of the water will contain a significantlyhigher percentage of suspended impurities, for reasons yet to beexplained. Consequently it is not advisable to return this part of thepond water to the pond.

The supply of air via the air supply pipe 8 causes the granularfiltering material 4 to be stirred and pushed up via the pipe 10. Afunnel 11 is provided for intercepting the filtering material 4.Eventually, the filtering material 4 exits the pipe 10 at the upper endthereof, after which the upward movement is stopped by the check member12 and the filtering material 4 will sink to the bottom of the reservoir2 again under the influence of the force of gravity. Because of theagitation to which the filtering material 4 is exposed, the slimyimpurities adhering to the filtering material will be detachedtherefrom. Said detached particles have a relatively low specific weightand will remain suspended in the pond water at the upper side of thereservoir. As already indicated above, this part of the pond water 5will eventually be discharged via the discharge pipe 15.

Once the filtering material has been cleared of the adhered impuritiesto a significant extent, the supply of air via the air supply pipe 8 isstopped and the membrane valve 20 is no longer energized, so that thewater can circulate via the circulation pipe 14 again and no new wateris supplied to the discharge pipe 15. The water level will fall fromlevel 18 to level 17 again. It stands to reason that fresh pond watermust be supplied to the reservoir to replace the pond water that hasbeen discharged via the discharge pipe 15.

Although the pipe 8 of the filtering system 1 is used for supplying air,said pipe might alternatively also be used for supplying a liquid, suchas water, and even pond water. In that case the granular filteringmaterial 4 will be agitated not by air but by a liquid flow movingupwards into the filtering material 4 via the pipe 8 and the pipe mouth9, to a significant extent via the pipe 10.

FIGS. 4 and 5 schematically show a filtering system 51 that likewisefalls within the scope of the present invention. FIG. 4 shows the normalusage of the system, whilst FIG. 5 shows a rinsing position that is usedperiodically, e.g. on a daily basis, for a short period, e.g. 5 minutes,depending on the expected degree of contamination. The filtering system51 shows a great deal of similarity to the filtering system 1. Thus thesystem likewise comprises a reservoir 52 having a V-shaped bottom 53,seen in vertical cross-sectional view. Present in the point of theV-shape is a passage 58 for pond water as well as for air, as willbecome clear hereinafter. A granular biological filtering material 54 ispresent at the bottom side of the reservoir 52, up to the levelindicated at 55. Pond water 56 is circulated through the reservoir 52 bymeans of a pump (not shown), with the pond water 56 entering thereservoir 52 via the inlet pipe 57 and the passage 58 and, during normaluse as shown in FIG. 4, exiting the reservoir 52 again via the returnpipe 59 that extends from the upper part of the reservoir 52 andreturning to the pond in question. In the reservoir 52, the pond water56 passes the filtering material 54, as a result of which the filteringmaterial 54 is cleared of impurities adhering thereto. The upper surface64 a of the water is at the same level as the inlet opening 65 of thereturn pipe 59.

To remove the impurities adhering to the filtering material 52 from thefiltering system 51 so as to ensure a correct operation of the filteringsystem 51 also after a prolonged period of time, the filtering system 51can be placed in the rinsing position as shown in FIG. 5. To that end,the air valve 59 that is connected to a pneumatic supply pipe 64 isswitched over. In the normal operating position, the valve 60 ispneumatically energized via valve 59 and pneumatic pipe 61 whichconnects to valve 59. In this energized condition of the valve 60, acentral pipe 61 is closed at the upper end thereof (FIG. 4). Said upperend is positioned above the level 55 of the filtering material 54. Onthe one hand, the energized condition of the valve 60 is terminated byswitching over the valve 59, as a result of which the valve 60 movesupwards to a limited extent and the upper end of the pipe 61 is opened.On the other hand, the valve 62 is pneumatically energized via the pipe63, as a result of which, in the first place, the inlet opening 65 ofthe return pipe 59 is closed, which in turn leads to the level of thewater 56 rising to the level 64 b when pumping is continued, which level64 b is the level of the discharge pipe 66 that opens into a sewersystem.

In the second place, air is supplied to the passage 58 via the pipe 67that branches off the pipe 63, from which passage 58 the air will flowupwards through the pipe 61, as the upper end thereof is open. Duringsaid flow, the air causes the impurities to become detached from thefiltering material 54 through which the air passes. Furthermore,filtering material will be carried along by the air flow. To support theinterception of air and filtering material in the pipe 61, the pipe 61is flared at the bottom end. Once the filtering material exits the pipe61 at the upper side, its relatively high specific weight will cause itto quickly settle on the upper side of the filtering material 54 againunder the influence of the force of gravity. The valve 60 functions as aresistance element for stopping the upward movement of the filteringmaterial. At the same time the filtering material 54 will move along thebottom 53 to the passage 58. Thus a circulation of filtering material 54through the pipe 61 is created, so that all the filtering material 54 issubjected to the rinsing action of the air flow in the pipe 61. Thedetached impurities are much lighter than the filtering material 54 andremain suspended in the pond water 56 above the filtering material 54,from which they will eventually be discharged to the sewer together withthe pond water 56 via the discharge pipe 66. Once the rinsing operationis complete and the impurities suspended in the water 56 have exited thereservoir 52, the valve 59 is switched over to the position that isshown in FIG. 4 again, so that the filtering system 51 will resume itsnormal filtering action again.

Various variants of the filtering systems 1 and 51 as described aboveare possible within the scope of the present invention. The main commonadvantage of these systems is the simple but very effective purifyingeffect thereof.

1. A device for removing impurities from a liquid, comprising areservoir for holding filtering material at a bottom side thereof andthe liquid, an upper side above the filtering material, a liquid supplychannel opening into the bottom side of the reservoir for supplying theliquid, to be purified to the reservoir, via a liquid displacementmeans, a first liquid discharge channel extending from the upper side ofthe reservoir for discharging purified liquid from the reservoir and afluid supply channel opening into the bottom side of the reservoir forcausing turbulence in filtering material present in the liquid bysupplying a fluid; using fluid displacement means, so as to detachimpurities from said filtering material, characterized in that a pipecomprising a first end positioned at the bottom side of the reservoirand a second end positioned opposite said first end is provided in thereservoir, spaced from the mouth of the fluid supply channel, for thepassage of a the fluid supplied to the reservoir via the fluid supplychannel.
 2. A device according to claim 1, characterized in that thepipe is provided with a funnel on the side facing towards the mouth ofthe fluid supply channel, which funnel flares out in the direction ofthe mouth of the fluid supply channel.
 3. A device according to claim 1,characterized in that the second end of the pipe is disposed in theupper side of the reservoir.
 4. A device according to claim 1,characterized in that a resistance element is disposed in the reservoir,spaced from the second end of the pipe and being in line therewith.
 5. Adevice according to claim 1, characterized in that the fluid supplychannel opens into the bottom of the reservoir.
 6. A device according toclaim 5, characterized in that the bottom of the reservoir extendsupwards from the mouth of the fluid supply channel.
 7. A deviceaccording to claim 6, characterized in that the bottom of the reservoiris substantially V-shaped, seen in vertical cross-sectional view.
 8. Adevice according to claim 1, characterized in that the mouth of thefluid supply channel in the reservoir is directed upwards.
 9. A deviceaccording to claim 1, characterized in that the device comprises asecond liquid discharge channel extending from the upper side of thereservoir for discharging liquid, with impurities suspended therein as aresult of the turbulence of the filtering material, and shut-off meansfor shutting off the first liquid discharge channel and/or the secondliquid discharge channel.
 10. A device according to claim 9,characterized in that a weir is provided between the first liquiddischarge channel and the second liquid discharge channel.
 11. A deviceaccording to claim 9, characterized in that the fluid displacement meansand the shut-off means are arranged for joint operation.
 12. A deviceaccording to claim 1, characterized in that said shut-off means operatespneumatically.
 13. A device according to claim 1, characterized in thatsaid shut-off means comprises a membrane.
 14. A device according toclaim 1, characterized in that the fluid supply channel causesturbulence in filtering material present in the liquid at regularintervals.